1. Field of the Invention
This invention relates generally to the comminution and granulation of solid material. It relates more particularly to a comminuting or granulating apparatus for polymeric and like material comprising the combination of a rotary cutting element and a cooperating fixed cutting element. More specifically, it relates to such a fixed cutting element which has been modified for increased efficacy.
2. Prior Art
Solid material such as polymeric material is generally transported and sold in comminuted or granulated form. One major advantage therein is that the material in such a form can be readily fed into extrusion and like devices for subsequent forming operations. Moreover, the material in such a form can be easily measured by volume, and can be transported short distances by pressure or suction through conduits.
Of a large number of devices for cutting solid material such as polymeric material into very small pieces, the most satisfactory appear to be those comprising at least one fixed cutting element or bed knife positioned around the cutting circle of a rotary cutting element, which is often provided with plural blades. Examples of such devices are those specified and depicted in the following U.S. Pat. Nos.: 3,661,332; 3,790,093; and 3,897,016. Notwithstanding the efficacy of these and similar devices, they are found wanting in one very significant aspect, viz., the fixed cutting elements or bed knives are usually short lived. That is to say, these bed knives, which are fabricated from construction metals and alloys of all kinds, as well as from very hard materials such as ceramics, must be removed for sharpening or even complete replacement after but a few days of use. Furthermore, the interruptions in operation caused by such sharpenings and replacements result in significant reductions in daily output, which are completely undesirable, especially in view of today's requirements for enhanced speed and improved efficiency in every stage of all manufacturing operations.